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1.
The phosphorus fractions in three tropical mangrove systems of Cochin region were analysed by sequential extraction method. Iron-bound phosphorus was the major fraction in the first two stations, while station 3 was exclusively dominated by calcium-bound phosphorus. Compared to other stations, about tenfold increase in total phosphorus content was observed at station 3. This station is a congregation of communally breeding birds, and there is accumulation of bird guano. Mineralogical analysis showed the presence of monetite, a thermodynamically metastable calcium phosphate mineral, in this unique system. The excreta and carcass of the birds in this sanctuary seems to be the reason for the formation of monetite, which is favoured by periodic fluctuations in redox potential. The high mass percentages of calcium and phosphorus by XRF and SEM–EDS analysis confirm the existence of calcium phosphate mineral at station 3. First two stations did not show any noticeable difference in phosphorus fractions and inorganic fractions constituted to about 65% of total phosphorus. But at station 3, inorganic fractions were about 92%. Low C:P ratios and low organic phosphorus content indicated active mineralisation of phosphorus at station 3. Bioavailable fractions of phosphorus at stations 1 and 2 were about 75%, whereas 98% of the total phosphorus was bioavailable at station 3. Since the bulk of the total phosphorus is bioavailable, these mangrove sediments have the potential to act as source of phosphorus to the overlying waters.  相似文献   

2.
Concentrations and vertical distributions of total nitrogen (TN), total phosphorus (TP) and their different forms in sediments obtained from nine locations of Lake Dalinouer in September 2008 were analyzed. The results demonstrated that TP in surface sediments ranged from 0.493 to 0.904 g/kg, and inorganic phosphorus was the main fraction of total phosphorus, ranging from 335 to 738 mg/kg. Simultaneously, the autogenetic calcium phosphorus (ACa-P) was the main fraction of inorganic phosphorus, ranging from 145.4 to 543.2 mg/kg. Vertical distribution of different phosphorus forms in different sediment cores was distinguishing, and most of them tended to increase toward the surface sediment, indicated that the phosphorus concentration was related to the humanity with a certain extent. The relationships between TP and occluded phosphorus and ACa-P were significant. Nitrogen in the sediment was composed mainly of organic nitrogen, accounting for grater than 80 % of TN. NO3 ?-N was the dominate fraction of inorganic nitrogen in the surface sediment, ranging between 51 and 346 mg/kg (151.1 ± 104.4 mg/kg), and accounting for between 2.2 and 17.7 % of total sediment nitrogen (6.2 ± 5.6 %). The ratio of organic carbon and TN in sediment was in range of 6.0–25.8 and presented a tendency of lake centre >lake sides, indicating that nitrogen accumulated in the sediments from lake sides came mainly from terrestrial source and nitrogen was mainly autogenetic in lake centre. Ratio of N:P in all sampling sites was below 14, indicated that N was the limiting nutrient for algal growth in this lake.  相似文献   

3.
Sediment phosphorus (P) fractions and profile distribution at submerged macrophyte growth zone, emergent macrophyte growth zone and open-water zone were studied in Wuliangsuhai Lake, China, as well as the correlations among water content, grain size, and organic matter and P fractions. Among the three surveyed zones, the highest concentrations of most P forms occurred in the surface sediment and the lowest between a depth of 12 and 22 cm, except HCl-P and NaOH-P. Sediment phosphorus was mainly associated to inorganic forms (>50%) in three surveyed areas, and the highest value of inorganic phosphorus (IP) in the surface sediment was obtained from submerged macrophyte growth zone. Submerged and emergent macrophytes increased the IP content by 107 and 44 μg/g, respectively, in the surface sediment compared with open-water zone. Vertical profiles of IP in the three surveyed zones showed that the concentrations decreased from surface to 12 cm depth and then increased. There was a similar trend in the sediment profiles of organic phosphorus (OP) and total phosphorus (TP), but the highest concentration of OP and TP in surface sediment was obtained from the emergent macrophyte growth zone. Compared with open-water zone, the emergent macrophyte increased TP content in surface sediment by 1.73 times to 1,320 μg/g, while submerged macrophyte enhanced TP content in the surface sediment by 1.13 times to 865 μg/g. It was observed that in macrophyte growth zones, a strong linear correlation existed between organic matter and OP (r > 0.98), and the maximum concentrations of OP were present in the areas with maximum concentrations of organic matter. Results show that, although rooted macrophyte could uptake directly P from sediments, it is responsible for increasing the internal P loading especially OP by reducing current velocities, attenuating wave energy and generating organic residue in Wuliangsuhai Lake.  相似文献   

4.
对崇明东滩采集的表层样和柱状样品，进行样品的总磷(TP)、无机磷(IP)和有机磷(OP)以及有机质含量等的测定，分析了磷的分布变化特征并对其影响因素和环境意义进行了探讨。  相似文献   

5.
Allochthonous inputs of suspended particulate matter from freshwater environments to estuaries influence nutrient cycling and ecosystem metabolism. Contributions of different biogeochemical reactions to phosphorus dynamics in Tomales Bay, California, were determined by measuring dissolved inorganic phosphorus exchange between water and suspended particulate matter in response to changes in salinity, pH, and sediment redox. In serum bottle incubations of suspended particulate matter collected from the major tributary to the bay, dissolved inorganic phosphorus release increased with salinity during the initial 8 h; between 1–3 d, however, rates of release were similar among treatments of 0 psu, 16 psu, 24 psu, and 32 psu. Release was variable over the pH range 4–8.5, but dissolved inorganic phosphorus releases from sediments incubated for 24 h at the pH of fresh water (7.3) and seawater (8.1) were similarly small. Under oxidizing conditions, dissolved inorganic phosphorus release was small or dissolved inorganic phosphorus was taken up by particulate matter with total P content <50 μmoles P g?1; release was greater from suspended particulate matter with total phosphorus content >50 μmoles P g?1. In contrast, under reducing conditions maintained by addition of free sulfide (HS?), dissolved inorganic phosphorus was released from particles at all concentrations of total phosphorus in suspended particulate matter, presumably from the reduction of iron oxides. Since extrapolated dissolved inorganic phosphorus release from this abiotic source can account for only 12.5% of the total dissolved inorganic phosphorus flux from Tomales Bay sediments, we conclude most release from particles is due to organic matter oxidation that occurs after estuarine deposition. The abiotic, sedimentary flux of dissolved inorganic phosphorus, however, could contribute up to 30% of the observed net export of dissolved inorganic phosphorus from the entire estuary.  相似文献   

6.
This study addresses the distribution of total phosphorus (TP) and its inorganic (IP) and organic (OP) fractions, grain-size and organic matter of surface and recent sediments, coupled to the behavior of total and dissolved inorganic phosphorus (TP and DIP) of the water column, of the semi-pristine Guaratuba Bay estuary, SE Brazil. Surface sediment samples were taken at 43 sites spread along the estuarine gradient and recent sediments from 3 short (35 cm long) cores from the upper, central and lower portions of the estuary, respectively. Highest TP and IP concentrations of surface sediments were detected within the upper sector and the transition zone between the upper and central sectors, all characterized by fine sediments, low salinities and water depths. In contrast, the lower sector and its narrow and deep tidal channel, subject to more intense tidal forcing, exhibited a higher fraction of sandy sediments with lower TP, IP and OP contents. In spite of the spatial variability in sediment grain size, IP corresponded to the major fraction of TP in all estuarine sectors and both TP and IP correlated significantly with the fine sedimentary (silt + clay) grain-size fraction. The fine surface sediments acted as a trap for IP at the fresh water–low salinity interface, which also corresponded to the region of a DIP sink in surface waters. In general, the short sediment cores showed that TP and IP contents increased from 15 cm depths to the top layer. Published sedimentation rates from additional cores taken at the sites of the short cores of this study, implied that depositional alterations of TP and IP increased during the early 1970s, which corresponded to the onset of anthropogenic disturbances from crop plantations in the lowland plains of the river end-member and urbanization at the estuary’s mouth and along the adjacent coast.  相似文献   

7.
In this study, bacterial community compositions in seven different estuarine sediments of Poyang Lake were analyzed using 16S rRNA gene-targeted metagenomic approach. Remarkable differences in the bacterial diversity were observed in these different estuarine sediments. Le, Chang and Rao river samples exhibited the higher bacterial diversity; the Fu river sample showed the less diversity. Bacterial richness and diversity were positively regulated by sediment inorganic phosphorus, and nitrite nitrogen, total phosphorus and inorganic phosphorus were found to be important drivers for bacterial community compositions. Proteobacteria, Acidobacteria, Firmicutes, Chloroflexi, Bacteroidetes, Planctomycetes, Gemmatimonadetes, Actinobacteria, Nitrospirae, and Verrucomicrobia were the major components of sediment bacterial communities. Among them, Proteobacteria was the most dominant phylum, followed by Acidobacteria and Firmicutes. Our study gives a comprehensive insight into the structure of bacterial community of the different estuarine sediments of Poyang Lake, indicating that the environmental factors played a key role in influencing the bacterial community composition in the freshwater ecosystem.  相似文献   

8.
Total organic nitrogen (TON) and phosphorus (TOP) were measured as a function of depth in 14 cores taken from a New England, tidal, freshwater marsh. TON and TOP ranged from 1.56 to 1.97% and 0.11 to 0.30% of dry weight sediments, respectively. The variation in both pool sizes over time was small and TON varied inconsistently with depth; however, TOP decreased regularly down to 20 cm. Consequently, the TON: TOP ratio increased linearly from 14∶1 at the surface to 32∶1 at 20 cm, then was nearly constant to 70 cm. This pattern may be a general feature of marsh sediments and may indicate 1) that phosphorus is recycled less efficiently than nitrogen, 2) that over time proportionately more introgen than phosphorus is incorporated into recalcitrant compounds, or 3) that phosphorus is more mobile than nitrogen in these marsh sediments. The total inorganic nitrogen pool was measured in this marsh also and was dominated by ammonium (97% of total). The annual average free ammonium concentration was 3.70±0.64 mg N per 1 at the surface and decreased to 0.92±0.18 mg N per 1 at 20 to 22 cm in the sediments. Sorptiondesorption studies showed that, on a fresh sediment volume basis, sediment sorbed ammonium was roughly equivalent to free porewater ammonium (K=0.8). The relationship between free and sorbed ammonium was linear between 0.4 and 24.0 mg NH4·N per 1 of pore water. The depth distribution of ammonium in these sediments is probably maintained by a dynamic balance between net microbial mineralization of litter, plant uptake, transpiration, diffusion, and porewater advection.  相似文献   

9.
Examination of small-scale spatial variation in essential to understanding the relationships between environmental factors and benthic community structure in estuaries. A sampling experiment was performed in October 1993 to measure infauna association with sediment composition and salinity gradients in Nueces Bay, Texas, USA. The bay was partitioned into four salinity zones and three sediment types. Higher densities of macrofaua, were found in sediments with greater sand content and in areas with higher salinity. High diversity was also associated with high homogeneous salinity (31–33‰) and greater sand content. Macrofauna biomass and diversity were positively correlated with bottom salinity, porewater salinity, and bottom dissolved inorganic nitrogen (DIN). Furthermore, species dominance shifted along the estuarine gradient.Streblospio benedicti dominated at lower salinity, but,Mediomatsus ambiseta andMulinia lateralis were the dominant species at higher salinity. Statistical analyses revealed significant correlations for sediment characteristics (i.e., increased fine sediments, water content, and total organic carbon) with decreased total abundance and diversity. Increased salinity and DIN were correlated with increased total biomass, diversity, and macrofauma community structure. These physico-chemical variables are regulated by freshwater inflow, so inflow is an important factor influencing macrofauna community structure by indirectly influencing the physico-chemical environment.  相似文献   

10.
Bioavailable phosphorus (BAP) plays an important role in phosphorus (P) release from lake and river sediments, as well as serves as an indicator for the potential P-release risk in sediment. Developing a feasible model which could predict BAP via other P fractions is needed for the lakes and reservoirs without regular BAP monitoring. The algal available P (AAP), NaHCO3 extractable P (Olsen-P), water soluble P (WSP) and readily desorption P (RDP) are four fractions of BAP. The vertical and spatial distributions of BAP fractions of three sediment cores from Jiulongkou Lake were analyzed. In addition, the P fractions, including total P (TP), organic P (OP), inorganic P (IP), non-apatite inorganic P (NAIP), and apatite P (AP) were measured to develop a model for predicting BAP. The model for each BAP fraction was developed based on datasets from Jiulongkou Lake and validated by the datasets collected from Wujin and Wugong Lake. The results showed that all of the four BAP fractions decreased with depth, along the direction of contaminant transport. Their rank order was AAP > Olsen-P > WSP > RDP in all samples. The concentration of BAP was affected by the anthropogenic input and aquatic macrophyte growth. Each of the four BAP fractions could be simulated by different P fractions: both AAP and Olsen-P were expressed by NAIP and OP, WSP had a significant relationship with OP, and RDP had significant relationship with IP. NAIP and OP were the major sources of the BAP fraction. The simulated results in two other lakes further illustrated that this model could be used to successfully predict the BAP concentrations in lakes in the study area, and holds promise for predicting the BAP levels in other lakes and reservoirs as well.  相似文献   

11.
The Xiangxi River is the first middling tributary of the Changjiang River near the Three Gorges Dam. The River is subject to phosphorus pollution mainly from industrial wastewater. As the water quality of the Xiangxi River could directly influence the water quality of the Three Gorges Reservoir, the research on phosphorus levels and its change in the sediment profile of the Xiangxi River could provide useful information in the dynamic changes in the system, thereby offering options for mitigative measures. Water and sediment samples from lower reaches of Xiangxi River were collected and the different forms of phosphorus in sediments of the Xiangxi River were studied. The concentrations of total phosphorus in sediment ranged from 757.67 to 1438.54 mg/kg. Inorganic phosphorus concentrations ranged from 684.63 to 1055.58 mg/kg. Phosphorus contamination was serious in some parts of the Xiangxi River. With an average concentration of 635.17 mg/kg, calcium-bound phosphorus is the main form among different inorganic phosphorus forms. Labile phosphorus and iron/aluminum-bound phosphorus measured 3.40, 0.05and 35.28 mg/kg, respectively. The mobilization potential of phosphorus of sediments was studied through adsorption and release experiments. The equilibrium concentration of phosphorus adsorption and release was around 0.1 mg/L. The initial concentrations of phosphorus in the overlying water and the sediments have obvious effect on phosphorus mobilization potential. In addition, the release rate of phosphorus in sediment increased with water depth.  相似文献   

12.
The Riogrande II reservoir in Colombia has a total storage capacity of 240 million m3 and lies 2,270 m above sea level. The reservoir is used for power generation, water supply and environmental improvement. Dissolved manganese (Mn) is removed from reservoir water dedicated to domestic use by purification processes. Removal of Mn, however, poses a major challenge to purification processes and warrants the study of ways to naturally reduce dissolved Mn levels in the reservoir. The source of Mn within the reservoir is not well understood, however, presumably arises from sediment mobilization initiated by variation in pH, redox potential (ORP or Eh), dissolved oxygen (O2) and ionic strength conditions. This study investigated conditions within the reservoir to further understand Mn transfer from the sediment into the water column. O2, pH, oxidation–reduction potential (ORP or Eh), organic matter content and electric conductivity were measured in water samples and sediment from the reservoir. Sequential extraction (SE) procedures were used to test the specific effects exerted by each of these conditions on Mn mobilization from the sediments. The European Community Bureau of Reference (BCR) sequential extraction procedure was used to quantify metals in sediment (referred to as the BCR extraction below). Statistical analysis of geochemical data from water samples (both water column and sediment pore water) and sediments demonstrated the conditions under which Mn can be released from sediments into the water column. The results indicated a primarily oxic water column and anoxic reducing conditions in the sediment (ORP or Eh ≤ ?80 mV). The pH of water in contact with bottom sediments varied from 7.6 to 6.8. The pH of sedimentary pore water varied from 6.8 to 4.7. The sediments contained significant amounts of organic matter (20 %). Chemical extractions showed that the exchangeable fraction contained over 50 % of the total Mn within sediments. Microscopic analysis using scanning electron microscopy–energy dispersive spectroscopy (SEM–EDS) indicated that Mn does not occur within well-crystallized mineral phases in the Riogrande II sediments. A large proportion of Mn exists instead as material adsorbed onto the surfaces of recently deposited sediment particles. Bacterial oxidation of organic matter may cause the observed anoxic conditions at the bottom of the reservoir. Mineralization of organic matter therefore contributes to reducing conditions within the sediments. Mobilization of Mn from the sediment into the water column may result from reductive dissolution of this fraction. Manganese release by this mechanism diminishes the water quality of the Riogrande II reservoir and warrants further study.  相似文献   

13.
太湖及其主要入湖河流沉积磷形态分布研究   总被引：57，自引：6，他引：57  
选择了我国第三大浅水湖泊--太湖及其主要入湖河流进行沉积磷形态的连续提取研究.太湖湖区沉积磷中不稳态磷(LP)及铝结合态磷(Al-P)含量很低,其余形态磷为铁结合态磷(Fe-P)＜钙结合态磷(Ca-P)＜有机磷(Org-P).河流沉积物中有机磷的相对含量高于湖泊沉积物,绝对含量平均值约为湖泊沉积物的3.9倍,铁结合态磷的绝对含量约为湖泊沉积物的3/4,湖区沉积物Fe-P含量与水体中PO3-4-、Chla呈显著正相关关系,同时与间隙水的氧化性呈显著负相关关系.太湖各湖区沉积物的磷形态表现为空间差异较大,活性组分的差异性要大于活性较差的组分.总的来说北部湖区沉积物中Fe-P和Org-P含量高于其他湖区,这与太湖北部湖区水体高营养级和藻类爆发关系密切.湖区沉积磷的垂直分布规律较复杂,既有随深度增加的,也有随深度降低的,河流沉积物同样如此.这与太湖及河流生态条件、污染物排放以及沉积动力学条件不同有关.  相似文献   

14.
Present study examined phosphorus dynamics through delineation of source as well as availability of phosphorus and its fractionation within the intertidal sediments of Pichavaram mangrove ecosystem. Twelve sediment samples and two cores were collected from the mangrove forest along with estuarine area (Vellar-Coleroon) during January 2005. Sediments were analyzed for total phosphorus and its fractionation using operationally defined chemical sequential extraction scheme (SEDEX). Dissolved phosphorus (in water) and total phosphorus (in sediments) concentrations were high in the Vellar region of Pichavaram mangrove area due to pollution load from nearby villages and agricultural fields. However, the spatial variation in dissolved phosphorus were insignificant (at significance level = 0.05). The results for the phosphorus fractionation (post-tsunami) were compared with earlier studies (pre-tsunami). It was observed that all phosphorus fractions (except adsorbed-phosphorus) showed a highly significant (at significance level = 0.05) increase in concentration after the tsunami event. There was significant decrease in the adsorbed phosphorus concentration as a result of tsunami. The changes were more pronounced for organic phosphorus which increased by almost twofold following the event. These variations were attributed to change in salinity, increase in dissolved oxygen as well as the retreat of tsunami water carrying the waste load. The vertical distribution of phosphorus through core sediments showed that mixing after tsunami had altered the different phosphorus fraction and its availability. Overall, the study indicated that the fluvial weathering along with litter degradation and anthropogenic sources controlled the biogeochemistry of phosphorus in this mangrove ecosystem. Observed changes in the concentrations are a result of altered physico-chemical characteristics caused by tsunami.  相似文献   

15.
Particulate carbon, nitrogen, and phosphorus samples from the water column and surficial sediments of the Maryland portion of Chesapeake Bay were thermally partitioned into their organic and inorganic components. During periods of both high and low fluvial input and high and low phytoplanktonic production, particulate organic carbon accounted for a mean of 99.3% of the total particulate carbon and particulate organic nitrogen accounted for a mean of 99.1% of the total particulate nitrogen. The particulate organic phosphorus contribution was variable both seasonally and spatially, accounting for 14–77% of the total pool of particulate phosphorus. The highest concentrations were found in the surface waters during maximum phytoplanktonic production and low fluvial input. The contribution of particulate inorganic phosphorus to the seston and to total particulate phosphorus decreased as distance from the primary fluvial source increased, reflecting a greater relative inclusion of particulate phosphorus in the biologically bound component in the higher salinity zone seaward of the turbidity maximum. Organic carbon and nitrogen constituted over 99% of the surficial sediment carbon and nitrogen, and organic phosphorus was 10–40% of the surficial sediment phosphorus.  相似文献   

16.
乌梁素海沉积物中全磷的分布特征   总被引：13，自引：1，他引：13  
开展了浅水草型湖泊乌梁素海沉积物中TP(全磷)的分布特征研究。结果表明,乌梁素海表层沉积物中TP含量在0.37~0.99 g/kg之间变化,平均值为0.75 g/kg;水平分布上,TP含量呈现从湖区四周向湖心递减的变化趋势,大部分湖区已具有生态毒性效应,并对湖区底栖生物群落和生态环境构成了较大威胁;垂向上,尽管沉积物中TP含量有所波动,但0~10 cm的表层沉积物中TP含量均随深度增加而递减,揭示了近年来人类活动的加剧对乌梁素海沉积物中磷累积的重大影响;实验得出了粉砂、粘土粒级>极细砂粒级>细砂粒级>中砂以上粒级的TP含量序列,各粒级对TP的吸附贡献率由吸附能力和质量百分比共同控制;磷的沉积对乌梁素海富营养化进程有深远影响。  相似文献   

17.
Chesapeake Bay sediments were examined for biogeochemical evidence of eutrophication trends using two mesohaline sediment cores. Measurements of 210Pb geochronology and sediment profiles of organic carbon, nitrogen, organic phosphorus, inorganic phosphorus, and biogenis silica (BSi) were used used to develop temporal concentration trends. Recent sediments have 2–3 times as much organic carbon and nitrogen as sediments from 80 to 100 yr ago, but the increases result from both changes in organic matter deposition and time-dependent changes in organic matter decomposition rates. Despite increases in phosphorus loading, no major changes in phosphorus concentration were noted throughout most of the century; anthropogenic phosphorus deposition, though not evident in sulfidic mid-bay sediments, must occur in more oxidizing sediment environments in both the northern and southern bays. Temporal trends in BSi concentrations are much less evident and the lack of substantial increases in this century suggest that BSi inputs may be capped by late spring-summer Si limitation.  相似文献   

18.
水体中富营养化水平与磷元素的赋存形态密切相关。目前围绕引起富营养化关键因子之一的磷形态的垂向分布特征、各磷形态间的迁移转化行为及其影响因素取得了比较明确的研究进展。为进一步揭示不同磷形态在沉积物-水体系中迁移转化行为随时空的变化特征,本文采用磷钼蓝分光光度法对沱江流域简阳段间隙水中可溶性活性磷(SRP)、可溶性非活性磷(SUP)及总溶解性磷(TDP)进行测定;采用SMT法和改进的沉积物无机磷形态连续提取法对沉积物中总无机磷(TIP)、总磷(TP)、难提取磷(Res-P)、可交换态磷(Exc-P)、铁结合态磷(Fe-P)、铝结合态磷(Al-P)、钙结合态磷(Ca-P)进行提取,磷钼蓝分光光度法进行测定,以揭示沉积物-水体系中磷的赋存形态垂向分布行为特征,并将实验数据与十年前该地区磷的赋存形态结果进行对比,探讨磷赋存形态的变化趋势及影响因素。结果表明:间隙水中SRP、SUP和TDP的含量分别为0.004～0.36mg/L、0.080～3.19mg/L和0.056～3.28mg/L;沉积物中TP、TIP、Res-P、Exc-P、Al-P、Ca-P含量分别为1235.40～1646.94mg/kg、860.00～1318.59mg/kg、130.31～537.13mg/kg、1.35～14.10mg/kg、0.007～0.12mg/kg、743.13～1109.91mg/kg,Fe-P未检出。对比十年前后沉积物-水体系中磷赋存形态的变化可知,由于受到外源磷输入的影响,间隙水中SRP、SUP以及TDP含量虽然在-10cm以上变化不明显,但在-10cm以下明显增大,且导致沉积物中TP、TIP含量增加;偏碱性的沉积环境导致Al-P的释放,其含量明显减小;Exc-P含量的减小与其转化为稳定的Ca-P或Res-P形态有关。研究认为:随着时空的变化,沱江简阳段沉积物呈现外源磷输入和内源磷释放的综合污染。总体而言,由于输入的磷形态大部分以稳定的Ca-P和Res-P形态存在于沉积物中,使得表层间隙水中生物可直接利用的磷含量总体变化不大,该地区富营养化程度不会加重。维持沉积环境的弱碱性,有利于Al-P、Exc-P等向Ca-P的有效转换,抑制河流富营养化。  相似文献   

19.
The adsorption of phosphorus on natural diagenetic iron (Feox) and manganese (Mnox) oxyhydroxides was studied in deep and littoral zone sediments of mesotrophic Lac Saint-Charles (46°56 N, 71°23 W), using a Teflon sheet technique for collecting diagenetically produced metal oxyhydroxides. Collected metal oxide amounts were greater at the deep-water station, relative to littoral zone stations reflecting sediment and local diagenetic differences. Two-layer surface complexation modeling on iron oxyhydroxide was consistent with the measured total P/Fe molar ratios except for the upper mixed Mn–Fe oxide layer from the littoral stations, where measured phosphorus exceeded the modeled phosphorus by more than fivefold. Soluble reactive phosphorus (SRP) exchange between oxyhydroxide samples and natural lake water in the laboratory revealed a labile phosphorus pool. Phosphorus determined on the Teflon sheets from the littoral zone stations appears to be related to a distinct non-humic organic carbon pool that readily exchanges SRP, while little exchange was observed from material collected from the deep-water station. We suggest that the enhanced SRP release from littoral zone sediments is due to an organic carbon and/or metal oxide-impoverished sediment matrix, limiting microbial oxide reduction and allowing phosphorus to be rapidly recycled at the sediment–water interface, instead of being slowly incorporated into humic material. The SRP fluxes revealed in our study, which originate from the solid phase at the sediment–water interface, would be difficult to resolve using interstitial pore-water samplers and might be a quantitatively important source of inorganic phosphorus in Shield lakes.  相似文献   

20.
Information on the chemical composition of phosphorus (P) fractions in sediments is fundamental to understanding P bioavailability and eutrophication in lake ecosystems. Phosphorus fractions and its bioavailability in sediments cores of Lake Hongfeng, southwest China, were investigated using a chemical sequential extraction scheme. Relationships between P fractions, P bioavailability and particle sizes were discussed. P fractions concentrations were ranked in the order: Residual-P > NaOH–rP > NaOH–NRP > HCl–P > BD–P > NH4Cl–P, and all of them decreased with increasing sediment depth. Statistical analysis showed that concentrations of bioavailable P (BAP) which includes the NH4Cl–P, BD–P, NaOH–rP and NaOH–NRP fractions ranged from 404.68 to 1,591.99 mg/kg and accounted for 26.8–71.8 % of the concentrations of total phosphorus (TP) in the top 5 cm sediments, whereas in the whole sediment cores, their concentrations ranged from 239.70 to 1,591.99 mg/kg and accounted for 26.8–76.0 % of TP. The results suggested that the sediments were a large potential source of P for algae blooms in Lake Hongfeng. Phosphorus fractions and their potential bioavailability were influenced by the sediment particle sizes, especially the bioavailability of the NH4Cl–P fraction, which was strongly affected by the presence of fine particle sizes in the sediments.  相似文献   

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